visual binary A visual binary is a gravitationally bound binary star system that can be resolved into two stars. These stars are estimated, via Kepler's third law, to have periods ranging from a few years to thousands of years. A visual binary consists of two st ...
Pictor
Pictor is a constellation in the Southern Celestial Hemisphere, located between the star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, and is an abbreviation of the older name Equuleus Pictoris (the "painter's easel ...
. It is too faint to be visible to the naked eye, having a combined
apparent visual magnitude
Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...
of 8.65. The two components have a magnitude difference of 3.7, and share a
common proper motion
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outsid ...
with an angular separation of , as of 2018. The distance to this system is approximately 136 light years based on parallax. It is drifting further away from the
Sun
The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...
with a radial velocity of +42.5 km/s, having come to within some 831,000 years ago.
The primary, component A, is a
K-type main-sequence star
A K-type main-sequence star, also referred to as a K-type dwarf or an orange dwarf, is a main-sequence (hydrogen-burning) star of spectral type K and luminosity class V. These stars are intermediate in size between red M-type main-sequence star ...
with a stellar classification of K1V and a visual magnitude of 8.82. Torres et al. (2006) classed it as a K1IV star, suggesting it is a
subgiant star
A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution o ...
that is
evolving
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation t ...
Sun's luminosity
The solar luminosity (), is a unit of radiant flux (power emitted in the form of photons) conventionally used by astronomers to measure the luminosity of stars, galaxies and other celestial objects in terms of the output of the Sun.
One nominal ...
from its photosphere at an effective temperature of 5,255 K. Its smaller companion, designated component B, is a red dwarf with spectral type M2V and apparent magnitude 12.33. It has a
projected separation
This glossary of astronomy is a list of definitions of terms and concepts relevant to astronomy and cosmology, their sub-disciplines, and related fields. Astronomy is concerned with the study of celestial objects and phenomena that originate outsid ...
of from the primary.
Companions
A planet,
HD 41004 Ab
HD 41004 Ab is an extrasolar planet approximately 139 light years away in the constellation of Pictor. It has mass 2.56 MJ planet
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available t ...
, was discovered by Zucker et al., in but not published until 2004. It has a mass >2.56 times that of
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...
. It orbits the primary star at a separation of 1.70
astronomical units
The astronomical unit (symbol: au, or or AU) is a unit of length, roughly the distance from Earth to the Sun and approximately equal to or 8.3 light-minutes. The actual distance from Earth to the Sun varies by about 3% as Earth orbits ...
, taking with a high
eccentricity
Eccentricity or eccentric may refer to:
* Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal"
Mathematics, science and technology Mathematics
* Off-Centre (geometry), center, in geometry
* Eccentricity (g ...
of 0.74.
HD 41004 Bb is a
brown dwarf
Brown dwarfs (also called failed stars) are substellar objects that are not massive enough to sustain nuclear fusion of ordinary hydrogen ( 1H) into helium in their cores, unlike a main-sequence star. Instead, they have a mass between the most ...
that at the time of the discovery was orbiting closer to the secondary star than any known extrasolar planet or brown dwarf (a=0.0177 AU), at only 145 km/s, because of its low-mass parent star, taking 1.3 days. Its orbit is circular despite the gravitational effect of HD 41004 A because of the tidal effect of the nearby star HD 41004 B. A search for
cyclotron radiation Cyclotron radiation is electromagnetic radiation emitted by non-relativistic accelerating charged particles deflected by a magnetic field. The Lorentz force on the particles acts perpendicular to both the magnetic field lines and the particles' mot ...
from the magnetosphere of Bb in 2020 did not find any, indicating the planet is either weakly magnetized, or the emission cone did not point to Earth at the time of observation.